In recent years, in the fields of environmental quantification etc., immunoassays (hereinafter abbreviated to IA) are frequently used because expensive devices and proficiency in the operation are not necessary.
However, the antibody used in IA, which acts specifically on a target substance to be measured, is a high-molecular protein, and thus the activity of the antibody is influenced by various substances exerting an influence on the protein, and as a result, quantifications are inaccurate in some cases.
On one hand, prior to measurement of a target substance existing in a very small amount in the order of ppb (part per billion) and ppt (part per trillion), concentrating the sample at high degrees may be necessary, and in such cases, the sample concentrated by a solid-phase extraction method (hereinafter also called solid-phase concentration) or by extraction with a solvent (hereinafter also called solvent concentration) is used to measure the target substance.
However, the test sample contains a wide variety of compounds in addition to the target substance, and thus when the test sample is concentrated by solid-phase concentration or solvent concentration, a compound exerting an influence on the antibody, that is, a substance interfering with the antigen-antibody reaction is also concentrated, and as a result, the activity of the antibody is influenced, resulting in abnormal values of quantifications in some cases.
One object of this invention is to provide a method of selecting an antibody which in measurement of the antigen by IA, is hardly influenced by an interfering substance with which a sample may possibly be contaminated, whereby occurrence of incorrect measurement in IA is prevented.
Another problem of this invention is to provide an IA kit with little occurrence of incorrect values by utilizing an antibody tolerant of or resistant to a substance interfering with the antigen-antibody reaction.